This filter provides a very flexible logger.
It is not designed as a logger, in order to be plugable only on
a sub-tree of the URL space (a logger would log all site accesses).
It provides as much details as you want, and uses a very simple format:
each log entry (or record is made of several lines having
the folowing format:
variable=value
A record starts with the special url variable value which
provides the requested URL.
This filter will compress the content of replies using GZIP or whatever
encoding scheme requested in the TE: header of the request.
Compression is done on the fly.